This invention relates to an automatic document feeder suitable for use with an electrophotographic copying apparatus for automatically feeding to an exposing station one document sheet after another from a stack of document sheets piled on a feeding tray by starting at the lowermost document sheet of the stack and returning the document sheets to the stack on the feeding tray and placing them on uppermost document sheet of the stack after the document sheets have been treated for exposure.
When a document consisting of a series of document sheets of several pages is copied by an electrophotographic copying apparatus, it is troublesome to repeatedly perform the operation of placing one document sheet on a contact glass member, setting a pressing plate thereon, removing the document sheet after it has been treated for exposure and replacing the illuminated document sheet for exposure by another document sheet of the next following page. To eliminate the need for the operator to perform this troublesome operation, proposals have been made to use an automatic document feeder which automatically feeds one document sheet after another from a stack of document sheets on a feeding tray and automatically ejects document sheets that have been treated for exposure.
When a document consisting of a multiplicity of document sheets of several pages is copied to produce a plurality of copies of the document, it is usual practice to place one document sheet on the contact glass member and produce a desired number of copies of the document sheet and repeat the same operation, until all the document sheets have been treated. The copies of the document sheets produced by the aforesaid operation and ejected from the copying apparatus are sorted either manually or by using a sorter to produce a desired number of copies of the document each copy consisting of copies of the document sheets arranged in the order of pages. In the automatic document feeder described hereinabove, the time required for feeding a document sheet to a predetermined position in an exposing station is short and substantially as long as the time required for a scanner to be restored to its original position. Therefore, if only one copy is produced each time one document sheet is fed to the exposing station and this is repeated until a copy each of all the document sheets is produced, then it is possible to produce a required number of copies of the document each copy consisting of copy sheets of the document sheets arranged in the order of pages merely by repeating the aforesaid operation a number of times corresponding to the desired number of copies of the document to be produced while eliminating the need to perform the operation of sorting the copies in the order of pages.
When this operation is performed, it will be possible to produce the required number of copies of the document by repeatedly feeding and returning the document sheets a number of times corresponding to the required number of copies of the document, if one document sheet after another is fed from the feeding tray by starting at the lowermost document sheet of the stack to the exposing station and the document sheets are returned to the feeding tray and placed on the uppermost document sheet of the stack after exposing is finished.
This type of automatic document feeder is known and disclosed in Japanese Patent Publication No. 56-467 corresponding to (U.S. patent application Ser. No. 671,867, filed Mar. 30, 1976) and Japanese Patent Publication No. 56-40338 corresponding to (U.S. patent application Ser. No. 523,610, filed Nov. 13, 1974), for example.
When a plurality of copies of a document consisting of a series of document sheets of continuously numbered pages are produced by using this type of automatic document feeder, it is necessary to monitor the feeding of the document sheets to the exposing station to determine how many number of times the document sheets have been fed to the exposing station and returned therefrom. To this end, the automatic document feeder disclosed in the Japanese patent publications referred to hereinabove is provided with a partition plate inserted into the feeding tray across the rear wall. A series of document sheets piled in a stack in which the first page of the series forms the lowermost document sheet and the next following pages are piled thereon in an orderly manner are initially placed on the feeding tray in such a manner that the partition plate is placed on the document sheet or the last page of the series. The document sheets are successively fed to the exposing station from the feeding tray by starting at the lowermost document sheet or the first page of the series and returned to the feeding tray, and when all the document sheets have been fed and no document sheet is left under the partition plate, the partition plate is detected by a sensor and a document sheet feeding completion signal is produced. When only one copy each of the series of document sheets is produced, the automatic document feeder is rendered inoperative by this signal. When a plurality of copies are produced, the partition plate is withdrawn from below the stack of document sheets when this signal is produced and placed on top of the stack of document sheets again. This operation is repeated a number of times corresponding to the desired number of copies to be obtained, so that the automatic document feeder is rendered inoperative after a predetermined number of copies of the document have been produced following sensing of the partition plate a predetermined number of times.
In the automatic document feeder of the aforesaid construction, a mechanism of complex construction should be provided for moving the partition plate each time the operation of feeding the series of document sheets to the exposing station is finished. Also, means should be provided for the operator to input to automatic document feeder data on the number of copies to be produced and whether only one surface or both surfaces of each document sheet should be copied.